Skin acts as a natural barrier between internal and external environments and therefore plays an important role in vital biological functions such as protection against mechanical and chemical injury, micro-organisms, and ultraviolet damage. The health and appearance of skin, however, can deteriorate due to environmental factors, genetic makeup, nutrition, and sun exposure.
With aging, the outer skin layer (epidermis) thins, even though the number of cell layers remains unchanged. The number of pigment-containing cells (melanocytes), however, decreases. Therefore, the skin appears pale and translucent. Large pigmented spots (age spots, liver spots, or lentigos) may appear in sun-exposed areas. Changes in the connective tissue reduce the skin's strength and elasticity. It is more noticeable in sun-exposed areas (solar elastosis). Elastosis produces the leathery, weather-beaten appearance common to farmers, sailors, and others who spend a large amount of time outdoors. Dehydration increases the risk of skin injury. Poor nutrition can also negatively impact the skin, causing dryness, rash, and puffiness.
Oxidative stress causes an increase in inflammation, a decrease in collagen levels, overexpression of the enzyme MMP, an increase in protein glycation, and an increase in mitochondrial decay throughout the skin. Additional aging processes include the intrinsic rate of proton leakage across the inner mitochondrial membrane, decreased membrane fluidity, and decreased levels and function of cardiolipin. The mitochondria, which create the energy the cells need by converting dietary and other cellular fuels into ATP, are adversely affected by these aging processes. It has been shown that oxidants generated by mitochondria are the major source of the oxidative lesions in the mitochondria that accumulate with age. (Ames B N, et al., Biochim Biophys Acta. 1995 May 24; 1271(1):165-70). In older skin, the mitochondria become severely impaired, and this leads to both a decrease in ATP production and greater oxidative damage.
Antioxidants are useful agents treating the skin from damage caused by chronoaging and photoaging. Useful antioxidants include those that provide the highest capacity to absorb free radicals. The oxygen radical absorbance capacity (ORAC) is a measurement of a materials ability to absorb free radicals (Dreher F, Maibach H. Curr Probl Dermatol. 2001; 29:157-64.). Antioxidants destroy harmful oxygen free radicals. Examples of Antioxidants include vitamins E, C, D, A, ferulic acid, neohesperidin dihydrochalcone, glutathione, melatonin, metallic zinc, beta-carotene, and numerous other compounds. Antioxidants scavenge oxidation of cells caused by oxygen free radicals, thereby preventing cell damage, and in turn protect the skin.